The present invention is related to suction and return line reservoir filters and, in particular, to a suction and return line reservoir having an improved cover to bowl seal integrity during suction operations, even under extreme negative pressures. While having a wide array of applications, such filters may be used to filter petroleum based fluids and may be installed at an opening on a wall of a tank or reservoir.
In the past, reservoir filters included a bowl having a first port which fit into a filter body having a second port. An access cover was attached to the top of the filter body in a sealed manner. A compressed spring or coil disposed between the access cover and a by-pass valve (friction fit to the top of a filter element, which in turn was in turn friction fit to the inner bottom surface of the bowl) was employed to force a flange at the rim of the bowl against a ledge on the filter body thereby maintaining a seal. While this arrangement is suitable for some positive pressure applications, operational difficulties are sometimes encountered in negative differential pressure suction operations. When a negative differential pressure suction operation is desired, the low pressure created in the cavity formed by the cover, filter body, and bowl urge the bowl toward the access cover against the biasing force of the spring. During such negative pressure suction operations, the spring may further compress thereby compromising the integrity of the seal between the filter body and the bowl. The elements of typical prior art filters of this type are shown in FIGS. 5a and 5b which illustrate the problem of the prior art filters.
Therefore, an object of the present invention is to provide a suction and return line reservoir filter that is suitable for use in negative differential pressure suction applications. In particular, an object of the present invention is to provide a positive means adapted to urge the bowl downward against the filter housing even during such high negative differential pressure suction operations.